Biomedical Engineering Reference
In-Depth Information
11.2.3 Proposal of Iso-contraction Exercise
Muscle contraction models proposed by A.V. Hill
et al
. present formulated linear
muscle movement extracted from living examples. In conventional isokinetic
training, joint rotation angles are constant and inner muscles are not contracted at
a uniform speed. To evaluate the relationship between muscle speed and tension,
we must model kinetic joint properties to adjust kinetic joint speed and maintain a
constant muscle contraction speed.
Figure 11.2
models simple kinetic elbow flexion, called an elbow flexion
model. The elbow is represented as two links of the forearm and upper arm,
making a single axial rotation in most cases. We consider the biceps brachii
and brachioradial muscles working in elbow flexion to be “working muscles”
because they develop considerable power. These two muscles are symmetrically
positioned anatomically around the elbow, so we use a single muscle model
integrating the properties of both (“Biceps Brachii Muscle” in the figure). In the
elbow flexion model,
angular speed [rad/s] of the
elbow.
L
denotes the length [m] of the biceps brachii muscle,
R
the length [m]
from the elbow to the origin biceps brachii muscle, and r the length [m] of the
lever arm. Based on this, L and
θ
denotes angles [rad] and
ω
ω
are calculated as follows:
R
2
L
=
+
r
2
+
2
Rr
cos
θ
(11.2)
−
Rr
sin
θ
dL
dt
√
R
2
ω
=
(11.3)
r
2
+
+
2
Rr
cos
θ
Expressing muscle-developed tension as
P
[N] and torque generated at the
elbow as
T
[Nm] yields the following:
√
R
2
r
2
+
+
2
Rr
cos
θ
P
=
T
(11.4)
Rr
sin
θ
To evaluations muscle strength that better matches outcomes of conventional
physiological research, we must maintain constant
dL/dt
rather than
as in con-
ventional isokinetic exercises, so we define constant
dL/dt
as an isokinetic muscle
contraction exercise, or iso-contraction exercise.
ω
Figure 11.2
Simple model of the elbow flexion.
